Synthetic turf has been used for years in athletic playing surfaces such as football, baseball, and soccer fields, and has more recently been used in other applications where an alternative to natural grass is desired. These applications include at least playgrounds, residential and commercial lawns and other landscaping, jogging paths, paintball fields, tennis courts, putting greens, and dog runs. Typically, synthetic turf includes a pile fabric having a backing and a plurality of upstanding ribbons, also called face fibers or filiform formations, resembling grass. Many synthetic turf products also include an infill material dispersed among the upstanding ribbons, which may consist of sand, tire rubber crumb, or other particulates, either singularly or in combination with each other. The infill material simulates the soil in natural turf, acts as a ballast, and/or contributes to the physical properties of the turf, such as resiliency, that make the turf suitable for a particular use.
Synthetic turf has a limited useful life, the length of which depends on the construction of the turf, the application for which it is used, and how the turf is maintained. As an example, a typical synthetic turf for use as an athletic field may have a useful life of from about 8 to 15 years. A large amount of synthetic turf is currently being used in hundreds of athletic fields and in other applications. To avoid sending that turf to landfills at the end of its useful life, there is a need for a method of recycling and reusing all or portions of the synthetic turf. There is also a need for a synthetic turf that is recyclable.
Recycling of a product typically refers to converting that product into a material or product for another use or extracting at least one of the individual components or materials of the product for use of that component or material in another product. The recycled product may be used in a similar product, such as when paper products are recycled to make other paper products, or may be used in a completely different product, such as when tires are recycled to make asphalt.
Methods for recycling carpet and for preparing carpet backing using recycled carpet scrap are known. Some such methods involve separating the carpet yarns, or tufts, from the backing, e.g. by cutting, and processing only the tufts to recover any nylon. In another recycling process the tufts can be spun into a new yarn for use in carpet or other textiles. One problem with these methods is that only the face fibers are recycled and the backing must be otherwise disposed of. Other methods of recycling carpets include grinding carpet scrap, including the backing, into a fine powder. The powder is then introduced into a carpet backing formulation which may be a precoat, laminate coating, skip coating, or foam coating. The formulation is then applied to a substrate, and cured by heating or drying. One problem with these processes for recycling carpet is that recycled material can make up only about 5% by weight of the carpet backing into which the recycled material is incorporated. This corresponds to approximately 2.5% by weight of a broadloom carpet.
Synthetic turf differs in composition from carpet, and those differences in composition make conventional carpet recycling processes unsuitable for recycling synthetic turf. The majority of carpet products use nylon face fibers, while the majority of current synthetic turf products use polyethylene. The primary coating of most broadloom carpet is a latex coating, while the primary coating in most synthetic turf is polyurethane. In the United States, only a small fraction of broadloom carpet includes a coating containing polyurethane, and only a small fraction of synthetic turfs have a coating containing latex.
Most of the synthetic turf manufactured in the past 6 years has had a polyurethane coating applied to the backing. There is a belief that polyurethane coated synthetic turf as a whole cannot be recycled. This is because the polyurethane coating, according to conventional wisdom, cannot be recycled. Polyurethane is thermoset (versus thermoplastic) and is therefore difficult and costly to recycle. Polyurethane is the reaction product of a polyol and an isocyanate. When these chemicals are mixed together and cured they form a solid polyurethane. The combination is applied to the backing of a tufted material for the purpose of locking the face fibers into the primary backing. An additional coating of a hot melt adhesive or a polyurethane foam can also be applied. This secondary coating is typically used to attach a secondary backing which can be polyester or polypropylene.
Many synthetic turf products include components that are not found in carpet and that are incompatible with, or at least undesirable in, conventional carpet recycling methods. For example, conventional carpet does not include infill. Typical infill materials for synthetic turf installations include sand, tire rubber crumb, and/or other particulates, either singularly or in combination with each other. Thus, recycling synthetic turf presents a unique problem not encountered in the recycling of carpet. Separating infill from the remainder of the turf may require use of special equipment, and there may be environmental concerns associated with disposing of the separated infill. Additional concerns in the recycling process are the effect of any residual infill particulates on the size reduction process and on the properties of the final product.
Conventional carpet recycling methods provide end products that are inconsistent with or that are not ideal uses of recycled synthetic turf. For example, nylon carpet recycling is focused primarily on separating and recovering the nylon, which is of greater value than other carpet components. In contrast, current synthetic turf typically contains little or no nylon. Additionally, conventional carpet recycling methods produce, as described above, a dry powder that can be incorporated in small amounts into carpet backings. Alternatively, for synthetic turf recycling, it is desirable to recover and reuse most or all of the synthetic turf, and to do so in a way that the recycled synthetic turf makes up a large percentage of the turf into which it is incorporated.
There remains a need for a method of recycling and reusing an existing synthetic turf, or at least a portion of an existing synthetic turf, to avoid sending the entire synthetic turf to a landfill when it is no longer useful. There is also a need for a synthetic turf that can be recycled and reused.